Prior art position transducers have taken many forms. One common type of transducer utilizes a flat or wirewound resistive element upon which a conductive slider or roller bears. Assuming the resistance per unit length of resistive element is known, by measuring the resistance between the slider or roller and the resistive element the position of the slider or roller along the resistive element with respect to one end of the element can be readily calculated.
However, such an arrangement has several disadvantages. Such transducers generally are not sealed, resulting in the accumulation of dirt and the formation of oxides on the resistive element which affects the contact resistance between the roller or slider and the resistive element. The build up of oxides and dirt causes inaccuracies in the resistance measured resulting in an inaccurate determination of position for an object coupled to the slider or roller. Further, a slider or roller directly in contact with the resistive element produces a high contact resistance resulting in further inaccuracies in the resistance measurement. While a certain amount of frictional contact between the roller or slider and the resistive element is beneficial in cleaning or "wiping" oxides and dirt disposed on the resistive element, too high a pressure, combined with direct contact of the roller or slider with the resistive element causes wearing of the outer surface of the resistive element leading to a shorter life for the element.
It is often desirable to measure the position or motion of an object which moves in a nonlinear manner, e.g. reciprocating motion, or to compensate for nonlinearities in a system. However, prior art position transducers are generally incapable of readily providing a nonlinear output relationship. In addition, it is often desirable to have a transducer which provides a selectable degree of positional resolution along selected portions of the transducer.